1. Field of the Invention
The present disclosure relates to a device and a method for evaluating a cement bond. More specifically, the present disclosure relates to a device and method for evaluating the thickness, quality, and presence of a cement bond. Yet more specifically, the present disclosure concerns a device and method for evaluating a cement bond between cement and formation.
2. Description of Related Art
Hydrocarbon producing wellbores typically comprise casing cemented within a wellbore. Cement bonds the casing to the wellbore and is added into the annulus between the casing outer diameter and wellbore inner diameter. The cement also isolates adjacent zones within a formation from one another. Isolating adjacent zones can be important when one of the zones contains oil or gas and the other zone includes a non-hydrocarbon fluid such as water. Should the cement surrounding the casing be defective and fail to isolate the adjacent zones, water or other undesirable fluid can migrate into the hydrocarbon producing zone thus diluting or contaminating the hydrocarbons within the producing zone.
The casing is subjected to mechanical loading cycles from applied pressure differentials and thermal loading that create internal and external stresses. Corrosive substances, such as salt water and sulfur containing compounds, to name a few, can erode casing structure and reduce its yield strength. Downhole logging tools and drilling bits can damage or also erode casing. Production casing may fail due to erosion, surface damage, its loading cycles, or combinations thereof. Identifying casing defects from erosion or other damage can reveal a potential failure. Casing damage is identifiable by various measures, such as by evaluating casing thickness. Examples of casing analysis devices include acoustic measurement tools, magnetic flux leakage apparatus; eddy current devices; and mechanical calipers.